Remove Duplicates from Activerecord has

I have the following database schema model for a Jukebox:

Artist
  has_many :albums
  has_many :tracks, through: :albums
Album
  belongs_to :artist
  has_many :tracks
Track
  belongs_to :album
  has_one :artist, through: :album
  belongs_to :genre
Genre
  has_many :tracks
  has_many :albums, through: :tracks
  has_many :artists, through: :albums

I want to be able to call .albums on an instance of the Genre class and return an array with one instance of each of the albums that has tracks with the associated genre_id.

What I'm getting is an array with duplicates of the same album instance for each track. E.G. if there are 10,000 tracks with the genre_id associated to "Rock", I'm going to get an array with 10,000 instances when calling .album, even if there's only 1000 unique albums within that array.

I'm trying to solve this for a challenge, so just running .all.uniq on the call won't be sufficient. I need to have something inside the class itself that will return the desired result when .all is run.

However, I can't find the ActiveRecord command that would essentially filter out the duplicates, and trying to write a separate class method doesn't seem to work either.

Disclosure - I've only been working with ActiveRecord for a few days. I hope the above is clear. Any help much appreciated!

CodePudding user response：

distinct should work for you:

genre = Genre.first
genre.albums.distinct

CodePudding user response：

Ahh - I eventually found the answer, thanks to this article: https://www.lugolabs.com/articles/distinct-active-records-in-has_many-through-associations

class Genre < ActiveRecord::Base
  has_many :tracks
  has_many :albums, -> { distinct }, through: :tracks
  has_many :artists, -> { distinct }, through: :albums
end